In recent years, in a transistor formation process, in order to reduce the resistance of the source and the drain, silicidation has been performed using a material such as Ni or Co to form NiSi or CoSi, respectively. In addition, for the reduction of junction leak current, an alloy in which 5 to 10% Pt or Pd is mixed into Ni or Co has been used. Especially, when NiPt is used, the improvement of heat resistance and a junction leak current suppression effect are expected. (see Patent Literatures 1 and 2)
In a silicidation step, by forming an alloy into a film on a Si substrate and then subjecting the alloy to thermal oxidation treatment, the alloy reacts with Si to form a silicide, but the remaining unreacted alloy needs to be removed. For example, a method using SPM (a mixed liquid of sulfuric acid and hydrogen peroxide) in order to remove unreacted NiPt after NiPt silicide formation is known. (see Patent Literatures 3 and 4)
In addition, as a cleaning method for dissolving NiPt, a method using aqua regia is known (see Patent Literature 5).
In addition, a method of treatment with a sulfuric acid-based oxidant followed by treatment with hydrochloric acid-based oxidant is proposed (see Patent Literature 6).
In addition, a method is known which uses a hydrogen peroxide solution, ozone water, or electrolyzed anode water in order to clean a semiconductor substrate while suppressing the corrosion of a metal film in cleaning the semiconductor substrate having the metal film (see Patent Literature 7), but the cleaning ability is insufficient for unreacted NiPt removal after silicide formation.